JP2708578B2 - Bonded magnet - Google Patents

Description

The present invention relates to a bonded magnet using a rare earth element-iron-nitrogen-hydrogen-oxygen-based magnetic material.

In particular, by controlling the crystallinity, particle size, composition and particle shape of this magnetic material powder, the magnetic properties of the powder are controlled,
The present invention relates to a bonded magnet produced by using an organic substance, an inorganic substance or a metal as a binder and compressing or injection molding or compacting the powder.

[Related Art] Bonded magnets have attracted special attention in recent years because of their good mechanical workability, magnets having complicated shapes and their ability to be integrally formed, and their industrial applications are expanding. Bond magnets using Sm ₁ Co ₅ or Sm ₂ Co ₁₇ magnetic materials, which are reliable sintered magnets for a long time, and Nd-Fe-B materials, which have recently gained a large market due to their high magnetic properties Is called a rare earth-based bonded magnet or a plastic magnet (hereinafter referred to as “Pramag”), and the market scale is expanding.

However, the Sm-Co system is a material that is physically stable because its components Sm and Co are both expensive and the supply is unstable, and is inferior in physical properties to the Nd-Fe-B system. regardless of,
It is being converted to Nd-Fe-B magnet for many applications. This tendency is not limited to sintered magnets, but is also common for plastic magnets. The Nd-Fe-B system is a sintered magnet whose (BH) _max
Is very high, 40MGOe or more, and Nd, Fe, and B are relatively inexpensive and have a stable supply. Therefore, demand is increasing in recent years, but there is a problem in corrosion resistance, and improvement in that point Is further desired.

Also, both of these two magnetic materials have disadvantages as a magnetic material for a bonded magnet or a plastic magnet. In other words, the mechanism of manifesting the magnetic properties of Sm ₂ Co ₁₇ and Nd-Fe-B systems greatly depends on the microstructure of the sintered body, and the difference in the composition between the inside and the grain boundary part or the precipitation phase in the grain boundary part Is essential for the development of high magnetic properties. Therefore, when crushed to a particle size of about several μm, which is convenient for kneading with the binder for the bonded magnet,
Deterioration of magnetic properties and corrosion resistance becomes remarkable. Also, a sample obtained by the Nd-Fe-B type super-quenching method has the drawback that fine particles can be prepared, but the magnetic properties are significantly lower than that of a sintered body, and only an isotropic magnet can be produced as it is.

Therefore, the Sm ₂ Co ₁₇ system needs to have a particle size of about 30 μm or more, and the Nd—Fe—B system requires a particle size of 50 to 100 μm, which is difficult to handle as a raw material powder for a bonded magnet. In the Nd-Fe-B system, hot press or diap set treatment is applied as an attempt to produce an anisotropic magnet using powder that can be used industrially, and a fine-grained anisotropic bonded magnet raw material powder is used. This has been studied and is becoming successful, but the problem of longer and more expensive processing steps remains.

[Problems to be Solved by the Invention] The present invention uses a magnetic material having high magnetic properties even when finely pulverized to about 2 to 3 μm (Japanese Patent Application No. 1-235822) to solve the above-mentioned problems in the prior art. It is an object of the present invention to provide a bonded magnet that solves the above problem.

Configuration of the present invention to solve the above problems [Means for Solving the Problems] (1) represented by the following composition formula, and rare earth elements have a substantially Th ₂ Zn ₁₇ structure - iron - A bonded magnet comprising a nitrogen-hydrogen-oxygen-based magnetic material.

Composition formula R _α Fe _{(100-α-β-γ-δ)} N _β H _γ O _{δ In the} above composition formula, represented by atomic percentage, 5 ≦ α ≦ 20 10 ≦ β ≦ 25 1.5 ≦ γ ≦ 53 ≦ δ ≦ 10 R is a rare earth element containing samarium as a main component.

(2) The magnetic powder material according to (1), wherein the magnetic powder material contains a magnetic material having a composition in which 0.1 to 49 atomic% of iron is replaced with cobalt. Bond magnet.

(3) The coercive force is 100 Oe to 15 kOe, the saturation magnetization is 5 to 15 kG, and the squareness ratio is 0.1 when the residual magnetization with respect to the saturation magnetization is taken.
The bond magnet according to the above (1) or (2), wherein the magnetic anisotropy is 0.1 to 0.7 when the magnetization in the direction perpendicular to the orientation direction of the sample is taken as the magnetic anisotropy.

The rare earth element-iron-nitrogen-hydrogen-oxygen-based magnetic material used in the present invention is the magnetic material described in the prior application (Japanese Patent Application No. 1-235822). It has the characteristic of having high magnetic properties. The basic property is that the magnetic properties can be expressed by ubiquitous or localized nitrogen, hydrogen and oxygen in the so-called 2-17 structure of rare earth element-iron. There is a characteristic that the magnetic characteristics can be controlled by changing.

Here, the 2-17 structure means Th ₂ Zn ₁₇ or Th ₂ Ni ₁₇
Refers to the structure. [Literature Handbook on the Physics and Chem
istry of Rare-Earths, Volume 2−Alloys and Inter-me
tallics (North-Holland Publishing Company, 1979) p.
6, Fig 13.3]. Lighter rare earths such as Sm which are more practical
_{Since it has a 2} Zn ₁₇ structure, a Th ₂ Zn ₁₇ structure is preferable in the present invention among the 2-17 structures.

Further, the rare earth element in the magnetic material of the present invention is preferably samarium. However, a rare earth element other than samarium may be present in a small amount as long as the object of the present invention can be achieved.

Accordingly, the present invention provides a coercive force of 100 Oe to 15 kOe and a saturation magnetization of 5 kOe prepared by taking advantage of the above characteristics of the magnetic material.
The present invention relates to a bonded magnet having a G to 15 kG, a squareness ratio of 0.1 to 0.99, and a magnetic anisotropy of 0.1 to 0.7.

Further, as the binder for the magnet, inorganic or metallic binders may be used in addition to the organic binders generally used.

<Manufacturing method> The first of the constitutional requirements of the present invention is a rare earth element-iron-nitrogen-hydrogen-oxygen-based magnetic material, and the second is that the magnetic properties of the magnetic material can be changed depending on the powder preparation conditions. In
Thirdly, there is provided a bonded magnet made of an organic, inorganic or metallic binder using the magnetic powder.

The first configuration requirement will be described below. However, it is not limited to this method. The process for producing a rare earth element-iron-nitrogen-hydrogen-oxygen-based magnetic material can be roughly divided into the following four stages.

(1) Preparation of rare earth element-iron-based master alloy (2) Coarse pulverization (3) Nitriding and hydrogenation (4) Fine pulverization, that is, adjustment of powder characteristics The following are general precautions.

The amount of oxygen and the amount of hydrogen can be controlled during the fine pulverization in (4), so that the characteristics of the magnetic powder can be changed.
Annealing to homogenize the composition after synthesizing the mother alloy in (1), and further homogenizing the composition and removing mechanical stress generated in the particles after nitriding and hydrogenating in (3) are magnetic properties. Is effective for improving

 Hereinafter, these steps will be described.

(1) Synthesis of mother alloy The raw material alloy can be prepared by a high-frequency furnace or an arc melting furnace, or by a liquid quenching method. The composition of the R-Fe mother alloy is preferably such that R is in the range of 5 to 25 atomic% and Fe is in the range of 75 to 95 atomic%. If the composition of R in the R-Fe master alloy is less than 5 atomic%, a large amount of α-Fe phase is present in the alloy, and a high coercive force cannot be obtained. On the other hand, if the composition ratio of R in the R—Fe master alloy exceeds 25 atomic%, a high saturation magnetic flux density cannot be obtained.

The composition range of R in the R-Fe-NHO magnetic material needs to be 5 to 20 atomic%. R is 5 atomic%
If it is less than 1, a high coercive force cannot be obtained, and if it exceeds 20 at%, a high saturation magnetization cannot be obtained.

Replacing iron with 0.1 to 49 atomic% of cobalt has the effect of improving the temperature characteristics of the magnetic characteristics. When the substitution amount of iron by cobalt is less than 0.1 atomic%, the effect of improving the temperature characteristics of the magnetic characteristics is not so much seen, and when it exceeds 49 atomic%, the saturation magnetization is undesirably lowered. In the case of cobalt substitution, cobalt is usually added at the time of producing this master alloy.

When a high-frequency furnace and an arc melting furnace are used, Fe is easily precipitated when the alloy solidifies from a molten state, which causes a decrease in magnetic properties, particularly, coercive force. Therefore, it is effective to perform annealing for the purpose of eliminating the phase of Fe alone and making the composition of the alloy uniform and improving the crystallinity. This annealing has a remarkable effect when performed at 800 ° C to 1280 ° C. The alloy produced by this method has good crystallinity and high saturation magnetization as compared with the liquid quenching method or the like.

Even with alloy manufacturing methods such as liquid quenching method and roll rotation method,
An alloy having a desired composition can be produced. In addition, the crystal grains of the alloy produced by these methods are fine, and submicron particles can be prepared depending on the conditions. However, when the cooling rate is high, the alloy becomes amorphous, and the saturation magnetization and coercive force do not increase as much as other methods even after nitriding or hydrogenating.
Also in this case, post-treatment such as annealing is necessary.

The mother alloy is 300-500pp regardless of the method of alloying
It contains about m oxygen. This level of oxygen content at this stage is what is introduced in the normal operation performed in the process.

(2) Coarse pulverization The pulverization at this stage may be a method of preparing only coarse powder such as a jaw crusher or a stamp mill, or a ball mill or a jet mill depending on the conditions. However, this pulverization is intended to uniformly perform nitriding and hydrogenation in the next stage, and it is necessary to prepare a powder state having sufficient reactivity in accordance with the conditions, and oxidation does not proceed. is important.

The amount of oxygen contained in the material after the coarse pulverization is 1000 ppm or less without much difference from the mother alloy.

(3) Nitriding and hydrogenation As a method for compounding or impregnating nitrogen and hydrogen in the pulverized raw material mother alloy, the raw material alloy powder is pressurized or heated in an ammonia gas or a reducing mixed gas containing an ammonia gas. The method is effective. The amounts of nitrogen and hydrogen contained in the alloy can be controlled by the mixed component ratio of the mixed gas containing ammonia gas, the heating temperature, the pressure, and the processing time.

As the mixed gas, any one of hydrogen, helium, neon, nitrogen, and argon, or a mixture of two or more of them and ammonia gas is effective. The mixing ratio can be changed in relation to the processing conditions, but as the ammonia gas partial pressure,
Especially 0.02-0.75atm is effective, processing temperature is 200-65
A range of 0 ° C. is preferred. The penetration rate is low at low temperatures, 650
At a high temperature of not less than ℃, iron nitrides are formed and the magnetic properties are degraded. In the pressure treatment, the contents of nitrogen and hydrogen can be changed even with a pressure of about 10 atm.

When a gas other than ammonia gas is used as a main component in the nitriding or hydrogenating atmosphere, the reaction efficiency is significantly reduced. However, if a long-term reaction is performed using a mixed gas of hydrogen gas and nitrogen gas, nitrogen and hydrogen can be introduced.

Nitrogen needs to be 10-25% by atomic percent. If it is less than 10%, the coercive force becomes extremely small.
On the other hand, if it exceeds 25%, the coercive force and the saturation magnetization are greatly reduced.

The nitridation / hydrogenation step is performed at a low oxygen partial pressure, but the amount of oxygen at the end of the step slightly increases to about 1000 ppm.

The amount of hydrogen in the composition formula is preferably in the range of 1.5 ≦ γ ≦ 5. If it is less than 1.5, the coercive force and corrosion resistance are low, and if it exceeds 5, the saturation magnetization is low and it is not practical.

(4) Fine grinding, that is, adjustment of powder characteristics The rare earth element-iron-nitrogen-hydrogen-oxygen based magnetic material in the present invention basically has a 2-17 structure of a rare earth element-iron system. Accordingly, the composition formula can be expressed as R ₂ Fe ₁₇ N _X H _Y O _Z. In the case of the same structure, the amount of X can exist stably up to about 4 to 5, but the coercive force also becomes 100 to 1500 Oe
Indicates a change in degree. The magnetic properties including the coercive force also show some dependence on the amounts of H and O, that is, Y and Z.
Of about 0.01 to about 1 and about 0.01 to about Z affect the properties of the powder obtained, including mechanical properties and corrosion resistance. Of these, the amount 0 is desirably in the range of 3 to 10% in terms of atomic percentage. If it is less than 3%, the coercive force and corrosion resistance are low, and if it exceeds 10%, the saturation magnetization is significantly reduced and is not practical.

The magnetic properties of the powder of the material having the above composition changed also vary depending on the particle size, crystallinity, and particle shape other than the composition. This is a result of a difference between a single magnetic domain particle diameter and an actual particle diameter or a difference in shape magnetic anisotropy. The pulverization step is a step relating to both the composition and the particle state.

Various methods such as a rotary ball mill, a vibrating ball mill, a planetary ball mill, a jet mill, and an Eiger mill can be used as the method of fine pulverization, but the magnetic material can be relatively easily pulverized to a particle diameter of several μm or less by any method. I can do it. Also, regarding the particle shape, the material of the grinding ball used for grinding,
Depending on the weight, number, type and amount of the solvent, and operating conditions of the apparatus, it can be prepared from a relatively acicular to a nearly spherical one.

From the submicron particle size as above, 10
When prepared up to 0 μm or more, coercive force is 100 Oe ~ 15k
Oe, various magnetic powders having a saturation magnetization of 5 to 15 kG, a squareness ratio of 0.1 to 0.99, and a magnetic anisotropy of 0.1 to 0.7 can be produced.

Next, a method for manufacturing a bonded magnet, which is a main component of the present invention, will be described.

 The following are five types of manufacturing methods.

The following binders can be used as usable binders.

As a first group, natural rubber, polychloroprene, nitrile / butyl rubber, polyisobutylene, silicone rubber, polyisoprene rubber and a mixture of two or more thereof.

Epoxy resin, phenol resin,
Synthetic rubbers, polyester resins, urea resins and mixtures of two or more thereof.

The third group is polyamide, polybutylene terephthalate, polyphenylene sulfide, liquid crystal polymer, polyphenylene oxide, polycarbonate, polyether sulfone, polyethylene, polypropylene, ethylene vinyl acetate copolymer, chlorinated polyethylene, elastomer, and soft vinyl chloride. The above mixture.

A fourth group is alumina cement, magnesia cement and mixtures thereof.

Fifth group Cu, Ag, Zn, Al, Ga, In, Sn, P
b, Bi metals and alloys of two or more thereof.

(A) Compression molding After adjusting the magnetic properties of the rare earth element-iron-nitrogen-hydrogen-oxygen-based magnetic powder, a corrosion resistance treatment, a coupling treatment and the like are performed, and an epoxy resin, a phenol resin, a synthetic rubber, a polyester resin, and a urea resin are used. And kneading with a required amount in a mold. At this time, a magnetic field may or may not be applied. After this is cured by heating, it is taken out of the mold and demagnetized or magnetized to obtain a product.

(B) Injection molding After adjusting the magnetic properties of the magnetic powder, the magnetic powder is subjected to a corrosion resistance treatment, a coupling treatment, and the like to obtain a polyamide, polybutylene terephthalate, polyphenylene sulfide, liquid crystal polymer,
After kneading and granulating polyphenylene oxide, polycarbonate, polyether sulfone, polyethylene, polypropylene, ethylene vinyl acetate copolymer, chlorinated polyethylene, elastomer, soft vinyl chloride, etc., and additives such as lubricants, injection using a magnetic field molding machine Molding. The product is further demagnetized or magnetized to produce a product.

(C) Compacting After adjusting the magnetic properties of the magnetic powder, additives such as a lubricant are added and kneaded, and then compacted using a mold. Take out this molded product, natural rubber, polychloroprene, nitrile
A solution obtained by diluting butyl rubber, polyisobutylene, silicone rubber, or polyisoprene rubber with toluene, ethanol, or the like is impregnated or press-fitted, and the solvent is evaporated to dryness. At any stage of these steps, demagnetization or magnetization is performed to obtain a bonded magnet.

(D) inorganic binder-bonded magnet After adjusting the magnetic properties of the magnetic powder, an additive such as a lubricant,
Alumina cement, magnesia cement, or the like, further diluted with a solvent or the like, are mixed and kneaded, and compression-molded with a mold or simply molded, and then the solvent is volatilized and dried. At any stage of these steps, demagnetization or magnetization is performed to obtain a bonded magnet.

(E) Metal binder bonded magnet After adjusting the magnetic properties of the magnetic powder, Cu, Ag, Zn, Al, G
a, In, Sn, Pb, Bi or a powder of a metal or two or more alloys, mixed and kneaded, put in a ceramic or metal mold, and compressed or heated and compressed. Thereby, a metal binder magnet having a relatively high density can be manufactured.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples.

Example 1 Sm and Fe having a purity of 99.9% were mixed so as to have a composition of Sm ₁₁ Fe ₈₉ , put in a ceramic crucible, melted at 1550 ° C. in a reduced-pressure Ar atmosphere of about −20 mmHg at 1550 ° C., and then cooled. F
Make an e-alloy ingot. Then add this ingot to 125
Anneal for about 3 hours in an Ar atmosphere at 0 ° C. to prepare a mother alloy having a composition of Sm _10.4 Fe _89.6 . The same mother alloy is almost Sm ₂ F in X-ray
e ₁₇ structure.

This alloy is pulverized by a coffee mill so that the average particle size becomes about 100 μm, and ammonia gas (0.35 atm)
After heating at 465 ° C. for about 2 hours in a mixed gas of hydrogen gas (0.65 atm), heating is performed at 465 ° C. for about 2.5 hours in an Ar gas atmosphere. The result is Sm _8.6 Fe _72.2 N _16.7 H _2.0 O
_{It is a 0.5} composition magnetic material. This powder is immersed in cyclohexane (dissolved oxygen concentration: 50 ppm, moisture: 80 ppm) and pulverized by a rotary ball mill to obtain a fine powder having an average particle size of about 2 μm. The oxygen content was controlled by the atmosphere when the powder was pulverized and the annealing after pulverization, and the final composition was changed to Sm _8.0 Fe _68.2 N _16.3.
H _2.7 O _4.8 . This powder has magnetic properties of a coercive force of 6500 Oe and a saturation magnetization of 11.5 kG.

0.5 g of this powder was mixed with 0.4 g of epoxy resin, transferred into a ceramic mold, and thermally cured in a magnetic field of 10 kOe. These compacts were magnetized with a magnetic field of about 60 kOe, and their magnetic properties were measured using a vibrating sample magnetometer (VSM), and the following results were obtained.

Coercive force (Hc) 6.5 kOe Remanent magnetization (Br) 5.2 kG (BH) max 4.2 MGOe Next, when the bending strength of this molded body was measured, 1340
It had a sufficiently practical strength of kg / cm ² .

Example 2 100 g of the powder of Example 1 and 50 g of nylon-6 were kneaded,
It is cut into 5-10 mm, about 7φ cylindrical chips, and is injected into a mold having a cross section of 3 mm × 12 mm at 300 ° C. in a nitrogen atmosphere by an injection molding machine to produce a rod-shaped molded body, which is subjected to a magnetic field of 60 kOe. Magnetized inside. The magnetic properties of the sample were measured using a vibrating sample magnetometer (VSM), and the following results were obtained.

Coercive force (Hc) 6.3 kOe Remanent magnetization (Br) 6.4 kG (BH) _max 6.7 MGOe Next, when the tensile strength of this compact was measured,
It had a sufficiently practical strength of 0 kg / cm ² .

Example 3 The annealing conditions of the Sm-Fe alloy ingot of Example 1 were changed. First, Sm annealed at 1094 ° C for 20 hours in Ar gas atmosphere
-Fe master alloy (A), Sm-Fe mother alloy (B) similarly annealed at 1094 ° C in an Ar gas atmosphere for 10 hours, and further 948 ° C in an Ar gas atmosphere
A Sm-Fe mother alloy (C) annealed for 32 hours is prepared. These master alloys (A), (B), and (C) were pulverized with a coffee mill so as to have an average particle size of about 100 μm. It was obtained _{(C) Sm 8.1 Fe 69.0 N} 17.3 H 1.8 magnetic material O _3.8 and a _{composition; 8.1 Fe 68.1 N 16.1 H 2.6} O 5.1; (B) Sm 8.0 Fe 70.0 N 16.0 H 1.5 O 4.5.

First, (A) the magnetic material was pulverized with a vibrating ball mill, and various powders were obtained by changing the pulverization time. Next, the (B) magnetic material, (C) magnetic material and (C ') magnetic material were pulverized using a rotary ball mill to obtain various powders. These powders are 5mm × 10mm × 2m under about 15kOe by uniaxial magnetic press
m molded body. These molded articles are immersed in a 2% by weight solution of isoprene rubber in toluene, and after sufficiently impregnated with the liquid, they are taken out and dried. The obtained magnet was magnetized in a magnetic field of 60 kOe, and the magnetic properties of these samples were measured using a vibrating sample magnetometer (VSM). The grinding conditions and magnetic properties for each sample are described below.

Example 4 The molded articles obtained in Examples 1 and 2 are referred to as molded articles A and B, respectively. These compacts were placed in a thermo-hygrostat and kept at a temperature of 80 ° C. and a humidity of 90% for 150 hours. As a result of visually examining the occurrence of rust, no rust was observed in any of the molded articles A and B.

[Effects of the Invention] As described above, the bonded magnet of the present invention has excellent magnetic properties as compared with conventional bonded magnets, and
Manufacturing is relatively easy.

Claims (3)

(57) [Claims] (1) The composition is represented by the following composition formula and is substantially Th
₂ A bonded magnet comprising a rare earth element-iron-nitrogen-hydrogen-oxygen based magnetic material having a Zn ₁₇ structure. Composition formula R _α Fe _{(100-α-β-γ-δ)} N _β H _γ O _{δ In the} above composition formula, represented by atomic percentage, 5 ≦ α ≦ 20 10 ≦ β ≦ 25 1.5 ≦ γ ≦ 53 ≦ δ ≦ 10 R is a rare earth element containing samarium as a main component. 2. The magnetic material according to claim 1, further comprising a magnetic material having a composition in which 0.1 to 49 atomic% of iron is substituted with cobalt.
The bonded magnet as described. 3. The coercive force is 100 Oe to 15 kOe, the saturation magnetization is 5 to 15 kG, and the squareness ratio is 0.1 to 0.1 when the residual magnetization with respect to the saturation magnetization is taken.
The bond magnet according to claim 1 or 2, wherein the magnetic anisotropy is 0.1 to 0.7 when the magnetization in the direction perpendicular to the magnetization in the orientation direction of the sample is taken.